1. Field of the Invention
The present invention relates to a manufacturing method of an actuator device, in which a vibration plate is provided on a surface of a passage-forming substrate including pressure generating chambers and in which piezoelectric elements are formed on the vibration plate, and relates to a liquid jet apparatus, in which droplets such as ink are ejected by displacement of the actuator device formed by the manufacturing method.
2. Description of the Related Art
An actuator device including piezoelectric elements which undergo displacement by being applied with voltage is applied to, for example, a liquid jet head ejecting droplets and the like. As the liquid jet head as described above, an inkjet recording head is known, for example. In the inkjet recording head, a part of pressure generating chambers communicating with nozzle orifices is formed by a vibration plate, and this vibration plate is deformed by piezoelectric elements to elect ink droplets from the nozzle orifices by pressurizing ink in the pressure generating chambers. There are two types of inkjet recording heads which have been put to practical use, which include: one applying a piezoelectric actuator device of a longitudinal vibration mode configured to expand and contract in an axial direction of the piezoelectric element; and one applying a piezoelectric actuator device of a flexural vibration mode.
In the former, volume of the generating chambers can be varied by making an end face of the piezoelectric elements abut on the vibration plate, and a head suitable for high-density printing can be manufactured. However, there arise the following problems: A troublesome process of making the piezoelectric elements correspond with an arrangement pitch of the nozzle orifices and cutting them into comb-like shapes becomes necessary; an operation of specifying and fixing the piezoelectric elements cut as described above for the pressure generating chambers also becomes necessary; and accordingly, the manufacturing process is complicated. Meanwhile, in the latter, the piezoelectric elements can be formed on the vibration plate by a relatively simple process, in which a green sheet as a piezoelectric material is attached in conformity to the shape of the pressure generating chambers and baked. However, there arises a problem that a high-density arrangement of the piezoelectric elements is difficult to perform since a certain area becomes necessary in applying the flexural vibration mode. Moreover, in order to eliminate the disadvantage of the latter, there is a type of head in which a uniform piezoelectric material layer is formed over an entire surface of a vibration plate by use of a deposition technique, this piezoelectric material layer is cut into shapes corresponding to the pressure generating chambers by use of a lithography method, and piezoelectric elements are formed so as to be independent for each of the pressure generating chambers.
As a material of the piezoelectric material layer constituting piezoelectric elements as described above, for example, lead zirconate titanate (PZT) is used. In this case, when the piezoelectric material layer is baked, lead components of the piezoelectric material layer diffuse in a silicon dioxide (SiO2) film which is formed on a surface of the passage-forming substrate made of silicon (Si) and constitutes the vibration plate. Thus, there arises a problem that a melting point of silicon dioxide decreases due to the diffusion of the lead components and thereby the silicon dioxide film melts due to the heat generated in baking the piezoelectric material layer. In order to solve the problems as described above, for example, there is one in which the zirconium oxide film constituting the vibration plate is formed on the silicon dioxide film and the piezoelectric material layer is formed on this zirconium oxide film to prevent the lead components from diffusing from the piezoelectric material layer to the silicon dioxide film (for example, see Japanese Unexamined Patent Publication No.11 (1999)-204849).
However, the zirconium oxide film has low adhesion properties with silicon dioxide film and therefore there arises a problem that delamination of the vibration plate or the like occurs. Namely, the zirconium oxide film is formed by forming a zirconium film by sputtering and thereafter subjecting the zirconium film to thermal oxidation. The zirconium film formed as described above takes the form of polycrystalline structure, but the crystals are likely to be formed into ball-shaped ones. Accordingly, even if there are column-shaped crystals, the rate of existence thereof is low, and therefore there arises a problem that the zirconium oxide film has low adhesion properties with silicon dioxide film and the delamination of the zirconium oxide film or the like occurs. Note that such problems as described above similarly arise not only in the actuator device applied to the liquid jet head such as the inkjet recording head but also in actuator devices applied to other apparatus.